The Diamonds were looking to level the series at one win apiece in Auckland following their 14-point defeat in game one, but were again outplayed, losing 63-52.
The world champions got to within seven in the final term, but the Silver Ferns kept their composure to seal the win.
Looking to mark Diamonds coach Stacey Marinkovich's 50th Test in charge with her first victory on New Zealand soil since 2021, the game didn't go to plan, with the world No.1 side crashing to their eighth straight loss across the Tasman.
Silver Ferns shooter Grace Nweke again proved lethal, slotting 47 goals from 51 attempts, but the home side's defensive pressure was also dominant.
Goal keeper Kelly Jury gave Australian shooters little room to move, while the midcourt, led by Maddy Gordon, stalled their supply to the goal circle.
The Kiwis again got off to a fast start and led 17-11, extending the buffer to 33-23 by half-time.
In the first half Marinkovich changed every position on court apart from goal shooter Sophie Garbin and centre Jamie-Lee Price, even making the rare move of benching skipper and wing attack Liz Watson at the end of the first quarter.
But the right combination proved elusive.
The only quarter the Australians won in Wellington was the third and they did the same on Wednesday night, outscoring the hosts by one goal.
It wasn't enough to make a significant dent on the deficit , with the Silver Ferns taking a 48-39 lead into the final term.
Goal attack Sophie Dwyer did her best to fire up her side, but they were still guilty of uncharacteristic errors that cruelled their chances.
Game three is in Perth on Sunday, followed by a Melbourne Test next Wednesday.
If the Diamonds manage to tie up the series with two wins in Australia, extra time will be played to decide the Cup winner for the first time, rather than goal differential.
Australia have only lost the trophy once in the past 10 series, going down in 2021.
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